NAVIGATIONAL SIGNAL TRACKING IN LOW POWER MODE

• US 20080150797A1
• Filed: 12/22/2006
• Published: 06/26/2008
• Est. Priority Date: 12/22/2006
• Status: Active Grant

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: CSR Technology Holdings Inc. (Qualcomm, Inc.)
• Inventors: Wang, Chi-Shin, Jia, Zhike, Kurethaya, Shridhara A.
• Granted Patent: US 7,847,726 B2
• Time in Patent Office: Days
• US Class Current: 342/357.06
• CPC Class Codes: G01S 19/24 Acquisition or tracking or demodulation of signals transmitted by the system synchronisation aspects of direct sequence spread spectrum modulation H04B1/7073
• CPC Class Codes: G01S 19/34 Power consumption

Abstract

The present invention provides systems and methods for navigational signal tracking in low power mode to conserve the power of handheld navigation receivers. In an embodiment, the receiver cycles between sleep and wakeup states. During the sleep state, most of the components of the receiver are powered off to conserve power, and during the wakeup state, the receiver tracks navigational signals. In an embodiment, the duty cycle of the sleep/wakeup states depends on the receiver dynamic state, e.g., whether the receiver is accelerating. In another embodiment, during the wakeup state, the receiver selects a tracking mode based on the signal strength. Under weak signal conditions, a tracking mode using a long integration to track the satellite signal is disclosed. In one embodiment, a tracking mode tracks the navigation signal by performing data aided integration using known or predicted data bits, such as the TLM and HOW words.

Claims

20. A navigational receiver, comprising:

an RF module for receiving a signal from a navigation satellite;

a baseband section coupled to the RF module for correlating the received signal with a locally generated replica; and

a processor, wherein the processor is configured to cycle the receiver between sleep and wakeup states, monitor a dynamic state of the receiver, determine a sleep time or duty cycle of the sleep and wakeup state based on the dynamic state of the receiver, select a tracking mode based on the strength of the received signal during the wakeup state, and track the received signal by performing data aided long integration on the correlated received signal during the wakeup state.

1. A method of tracking navigational signals at a receiving, comprising:

cycling between sleep and wakeup states;

monitoring a dynamic state of the receiver;

determining a sleep time or duty cycle of the sleep and wakeup states based on the dynamic state of the receiver;

selecting a tracking mode from a plurality of tracking modes based on received signal strength during the wakeup state; and

tracking a navigation signal by performing data aided long integration of the signal during the wakeup state.

2. The method of claim 1, wherein the data aided long integration is performed using known data bits of TLM and HOW words.

3. The method of claim 1, wherein the data aided long integration is performed over part of the total length of TLM and HOW words.

4. The method of claim 1, further comprising maintaining a sleep duration using a counter driven by a real time clock (RTC) in the receiver.

5. The method of claim 1, wherein the durations of the sleep and wakeup states depend on the dynamic state of the receiver.

6. The method of claim 1, further comprising waking up the receiver at a time coinciding with the start of TLM and HOW words in a signal.

7. The method of claim 1, further comprising extrapolating a position of the receiver during the sleep state.

8. The method of claim 1, wherein a RF module and baseband section of the receiver, including a DSP processor, are powered off during sleep state.

9. The method of claim 4, wherein the RTC is driven by a high accurate clock in a radio frequency section of the receiver.

10. The method of claim 4, wherein the RTC is calibrated by external timing or synchronization signal.

11. The method of claim 4, wherein the RTC is a standalone time keeping device.

12. In method of claim 1, wherein the plurality of tracking modes support different signal power levels.

13. The method of claim 1, wherein the selection of the tracking mode is based on the tracking signal strength.

14. The method of claim 4, wherein the RTC clock is calibrated during the wakeup state.

15. The method of claim 14, wherein the RTC is calibrated based on GPS time during the wakeup state.

16. The method of claim 4, wherein a single counter is used for calibration of RTC frequency and control of receiver wake up time.

17. The method of claim 1, further comprising downloading the current navigation data from the satellites when receiver conditions are favorable with enough battery power and signal strength, and absence of current navigation data.

18. The method of claim 17, further comprising decoding IODE (Issue Of Data Ephemeris) and IODC (Issue of Data Clock) data bits at fixed time intervals for change of associated data.

19. The method of claim 18, further comprising using Viterbi or other data bit prediction techniques to determine the IODE or IODC bits.

21. The receiver of claim 20, wherein the processor performs the data aided long integration using known data bits of TLM and HOW words.

22. The receiver of claim 20, wherein the processor performs the data aided long integration over part of the total length of TLM and HOW words.

23. The receiver of claim 20, further comprising:

a real time clock (RTC); and

a counter, wherein the counter is driven by the RTC to maintain a sleep duration for the sleep state.

24. The receiver of claim 20, wherein the durations of the sleep and wakeup states depend on the dynamic state of the receiver.

25. The receiver of claim 20, wherein the receiver wakes up at a time coinciding with the start of TLM and HOW words in a signal.

26. The receiver of claim 20, wherein the processor extrapolates a position of the receiver during the sleep state.

27. The receiver of claim 20, wherein the RF module and the baseband section of the receiver, including a DSP processor, are powered off during sleep state.

28. The receiver of claim 23, wherein the RTC is driven by a high accurate clock in a radio frequency section of the receiver.

29. The receiver of claim 23, wherein the RTC is calibrated by external timing or synchronization signal.

30. The receiver of claim 23, wherein the RTC is a standalone time keeping device.

31. The receiver of claim 20, wherein the tracking mode is selected from a plurality of tracking modes that support different signal power levels.

32. The receiver of claim 20, wherein the selection of the tracking mode is based on the tracking signal strength.

33. The receiver of claim 23, wherein the RTC clock is calibrated during the wakeup state.

34. The receiver of claim 33, wherein the RTC is calibrated based on GPS time during the wakeup state.

35. The receiver of claim 23, wherein a single counter is used for calibration of RTC frequency and control of receiver wake up time.

26-1. The receiver of claim 20, wherein the processor downloads the current navigation data from the satellites when receiver conditions are favorable with enough battery power and signal strength, and absence of current navigation data.

27-2. The receiver of claim 26, wherein the processor decodes IODE (Issue Of Data Ephemeris) and IODC (Issue of Data Clock) data bits at fixed time intervals for change of associated data.

28-3. The receiver of claim 27, wherein the processor uses Viterbi or other data bit prediction techniques to determine the IODE or IODC bits.

29-4. The receiver of claim 20, wherein the processor comprises a DSP processor and a RISC processor.

30-5. The receiver of claim 20, further comprising an accelerometer, wherein the processor uses the accelerometer to monitor the dynamic state of the receiver.